Switch actuating mechanism



Dec. 13, 1960 M. s. BLEMLY ETAL 2,964,600

SWITCH ACTUATING MECHANISM Filed May 1a, 1957 2 Sheets-Sheet 1 izibzv/Dec. 13, 1960 M. s. BLEMLY ET AL 2,964,600

SWITCH ACTUATING MECHANISM Filed May 16, 1957 2 Sheets-Sheet 2 INVENTORSMAAW/V o. 84 6/144 Y United States Patent C) SWITCH ACTUATIN G MECHANISMMarvin S. Blemly, Birmingham, and Adelbert J. Schenk, Huntington Woods,Mich., assignors to Jervis B. Webb Company, Detroit, Mich., acorporation of Michigan Filed May 16, 1957, Ser. No. 659,509

4 Claims. (Cl. 200-'47) This invention relates to an improvedconstruction for mounting and actuating a switch elementparticularly aswitch element of the sensitive push button type-to enable such' anelement to be used in industrial applications.

Switch elements of the type mentioned are widely employed for limitswitch uses, and in this application a need has existed for asatisfactory unit in which such a switch element can be mounted andactuated in response to the operation of moving components of machinery.Such a unit must impart the small amount of movement required foractuation of the switch element in response to contact between a movingmachinery part and an actuating arm. Contact forces are large as arecontacting movements relative to the amount of movement required foractuation of the switch element.

A number of constructions have been devised for such a unit. In generalthese include a housing in which the switch element is mounted, anactuating shaft joumalled in the housing with an actuating arm securedto a position of the shaft projecting from the housing, a cam carried bythe shaft and a cam follower. Some means are included for actuating theswitch element in response to movement of the cam follower.

The present invention offers a simplified arrangement of and relationbetween these elements which results in a greater degree of flexibilityof the unit particularly in terms of the amount of permissible movement,direction of movement and over-travel of the actuating arm, and whichwill provide improved service life under the conditions of use outlinedabove.

In the improved construction the cam follower is pivotally mounted inthe housing and includes a follower element mounted to contact theperiphery of the actuating cam which is formed with a notch to receivethe follower element and thereby define one position of the followerarm. Spring means are employed to bias the follower arm into contactwith the cam periphery and as a result the follower arm acts to defineone position of the actuating-cam when the element on the follower armis in engagement with the notch thereof. A centering spring is employedto urge the actuating shaft, actuating arm and cam to the centeredposition defined by the actuating arm. Preferably, this spring is a coiltype wound about the shaft and has its ends formed to extend-radiallyfrom the center of the shaft to provide a pair of action and reactionarms. A pair of members are provided, each being positioned to contacteither of the spring arms. One of these members is fixedly mounted inthe housing and the other is rotatable with the actuating shaft. As aresult these members and centering spring will return the shaft and camto a centered position for retention therein by engagement by thefollower element on the follower arm and the notch in the cam.

Preferably, one of the centering spring actuating mem bers is secured tothe cam and the other to the housing adjacent the cam and these membersare relatively positioned in spaced relation to the center of theactuating shaft and are in radial alignment with the center of the shaftwhen the cam is in its centered position.

The housing is made to provide very rigid support for the actuatingshaft and for the actuating arm.

An improved mounting of the actuating arm on the end of the shaft isalso provided so that the position of the arm relative to the centeredposition of the shaft and cam can be positively fixed in a great numberof positions.

A presently preferred constructional example of the invention is shownin the accompanying drawings which comprise the following views:

Fig. 1, a plan view of the construction with the housing cover beingbroken away;

Fig. 2, a sectional elevation taken on the line 22 of Fig. 1;

Fig. 3, an end elevation of the unit shown in Fig. 1;

Fig. 4, an enlarged sectional detail taken on the line 44 of Fig. 2; and

Fig. 5, a sectional detail taken on the line 55 of Fig. 4.

Referring to Figs. 1-3, the unit includes a housing having a base 10 anda cover 11. A switch element 12 and an actuating button 13 is secured tothe base by screws 14.

The base 10 includes a thickened, counterbored portion 16, mounting apair of ball bearings 17 and 18 which support an actuating shaft 19. Thebearings 17 and 18 are located by an intermediate spacer 20.

The inner-end of the shaft 19 projects beyond counterbored portion 16and a circular cam 23 is secured thereto. A coil centering spring 21 ismounted on the shaft 19 between the cam and inner-face 22 of thecounterbored portion. This spring is formed so that its ends 24 and 25extend radially outwardly from the center of shaft 19. These spring endsfunction as action and reaction arms in combination with a member 26secured to the cam and projecting toward the counterbored portion of thehous-- ing and a fixed member 27 mounted in the counterbored portion. Ascan be seen in Fig. 1, these members 26 and. 27 are mounted in spacedrelation to the center of theshaft 19 and are radially aligned with thecenter of the shaft with the parts in the position shown. A plate 28 issecured to the underside of the cam (Fig. 1) and acts as a stop incombination with the fixed member 27.

This position will be referred to as the centered position of thecomponents. It is additionally defined by engagement between a rollerfollower 30 carried by an actuating arm 31 and a notch 32 formed in theperiphery of cam 23 on the approximate radius of the roller follower 30.The actuating arm is secured to a collar 34 which is: pivotally mountedon a screw 35 engaging a boss 36 of the housing. The arm includes anL-shaped actuating tab 83 which is secured to the arm and projectsdownwardly to engage the push button 13 of the switch. A coil spring. ismounted on the collar 34 and normally urges the roller follower 30 intocontact with the periphery of the cam 23 through the reaction of one end40 of the spring against the housing and the other end 41 of the springagainst the tab 38.

The roller follower 30, notch 32 and the actuating cam and location ofthe tab 38 are inter-related with two considerations in mind, first, toimpart a proper amount of actuating movement to the switch push button13 upon movement of the roller follower out of the notch 32 and onto thecircular cam periphery; and second, to give sufiicient depth ofengagement of the roller follower 30 in the notch 32 so that thefollower arm will act to retain the actuating cam 23 and shaft 19 innormal centered position.

An actuating arm 44 is removably secured by set screws 47 to an armmounting member 45 which has a hub 46 mounted on the shaft 19 for freerotation. The hub is held on the shaft by a snap ring 48. The hubincludes a projecting circular portion 49 equipped with teeth 50' aroundthe outer circumference thereof. A square drive 52 (Fig. 5) is providedon the end of shaft 19 and a locking element 53 engages this squaredrive and is held on the end of the shaft by a screw 54. The lockingelement has an inwardly projecting portion 56 (Fig. 5) which hasinternal teeth 57 to engage the external teeth 50 of the hub 46. Thisarrangement offers a multiplicity of fixed radial positions of theactuating arm 44 on the shaft 19. For example, if the hub 46 is providedwith 25 external teeth 50 and the lock member 53 can be mounted in anyone of four positions on the square drive 52, a total of 100 positionsof the actuating arm are provided. In other words, the setting of thearm may be changed in increments of approximately 3% degrees.

While preferred embodiments have been described above in detail, it willbe understood that numerous modifications might be resorted to withoutdeparting from the scope of our invention as defined in the followingclaims.

We claim:

1. A switch construction of the type comprising a closed housing, ashaft journalled therein with at least one end of the shaft projectingfrom the housing and carrying an actuating arm, a cam mounted on theshaft in the housing, a cam follower arm pivotally mounted in thehousing and a switch element having an actuating button operable bymovement of the follower arm; characterized by a roller mounted on freeend of the follower arm for contact with the periphery of the cam, saidperiphery being generally circular and having an arcuate notch formedtherein on the approximate radius of said follower arm roller, springmeans normally urging said follower arm into contact with said camperiphery whereby said follower roller acts to retain said cam incentered position when engaged in said notch, switch actuating buttoncontacting means carried by said follower arm at a location between thepivot axis thereof and said follower roller, a coil centering springcarried by said shaft axially adjacent said cam, the ends of said springforming a pair of action and reaction arms extending radially of saidshaft, and a pair of action and reaction members positioned between saidspring ends in spaced relation on a radial line from the center of saidshaft, one of said members being mounted on said cam and the other beingfixedly carried by said housing whereby said centering spring willreturn said shaft and cam to centered position for retention by saidfollower arm after rotation of said actuating arm in either direction.

2. A switch construction of the type comprising a closed housing, ashaft journalled therein with at least one end of the shaft projectingfrom the housing and carrying an actuating arm, a cam mounted on theshaft in the housing, a cam follower arm pivotally mounted in thehousing and a switch element operable by movement of the follower arm;characterized by a follower element mounted on said follower arm forcontact with said cam, said cam having a circular periphery with a notchformed therein to receive said follower element and define one positionof said follower arm, spring means biasing said follower arm intocontact with said cam whereby said follower arm acts to define oneposition of said cam when the follower element engages the notchthereof, a centering spring carried by said shaft with the ends of saidspring forming a pair of action and reaction arms extending radially ofsaid shaft, a pair of members each positioned to contact either of saidarms, one of said members being fixedly carried by said housing and theother being rotatable with said shaft whereby said members and centeringspring will return said shaft and cam to the centered position definedby engagement of said follower element in the notch of said cam aftermovement of said actuating arm to produce rotation of said shaft ineither direction, and said housing having a counterbored portioncontaining a pair of bearings for supporting said shaft, one end of saidshaft projecting into said housing beyond said counterbored portionthereof, said cam being secured to the inner end of said shaft, saidcentering spring being mounted on said shaft between said cam and saidcounterbored housing portion, one of said spring contacting membersbeing secured to said cam and projecting toward the housing and theother of said spring contacting members being secured to the housing andprojecting toward said cam, said two members'being relatively mounted inspaced relation to the center of said shaft.

3. A switch construction according to claim 2 wherein said members arein radial alignment to the center of said shaft when said cam is in thesaid centered position.

4. A switch construction of the type comprising a closed housing, ashaft journalled therein with at least one end of the shaft projectingfrom the housing and carrying an actuating arm, a cam mounted on theshaft in the housing, a cam follower arm pivotally mounted in thehousing and a switch element having contact means operable by movementof the follower arm; characterized by a follower element mounted on saidfollower arm for contact with said cam, said cam having a notch formedtherein to receive said follower element and define one position of saidfollower arm, spring means biasing said follower arm into contact withsaid cam whereby said follower arm acts to define one position of saidcam when the follower element engages the notch thereof, means carriedby said follower arm for engaging said switch element contact means, acentering spring carried by said shaft with the ends of said springforming a pair of action and reaction arms extending radially of saidshaft, and a pair of members each positioned to contact either of saidarms, one of said members being fixedly carried by said housing and theother being rotatable with 'said shaft whereby said members andcentering spring will return said shaft and cam to the centered positiondefined by engagement of said follower element in the notch of said camafter movement of said actuating arm to produce rotation of said shaftin either direction.

References Cited in the file of this patent UNITED STATES PATENTS Shortet al Mar. 24, 1959

